The present invention relates to a sewing machine in general, and more particularly to a thread tension device of a sewing machine which is operated in association with a fabric presser lifting lever to be ready for positively receiving a thread to be adjustably tensioned for sewing a fabric.
The upper thread tension device of a sewing machine generally includes a pair of tension disks which are adjustably pressed against each other by a thread tension spring to clamp an upper or needle thread therebetween with an adjustable pressure to give the thread a desirable tension in dependence upon the kind of fabrics to be stitched, the type of threads to be used and/or the stitches to be selected. Each thread tension disc is usually finished with precision grinding on the thread holding face of the disc. When the tension device does not hold the thread and the thread tension discs are not given pressure, they are closely in contact with each other. Therefore, the thread must be held with an operator's both hands under tension for setting the thread between the discs. Contemporary sewing machines have the thread tension discs housed within a machine frame. With such a structure, the setting of the upper thread will be quite difficult. When the thread is loosened and the thread tension disc is separated from a thread tension base plate, the thread will drop into a space between the base plate and the tension disc.